Wheel bearings are what allows your wheels to keep turning smoothly. The have an extremely tough job to do and over time they will eventually start to wear out and make a very noticeable noise which you'll be able to hear clearly from inside the car. The noise(kind of a low drone or rumble) will get louder the faster you go. When a wheel bearing fails there are a number of other parts that should be changed at the same time, such as seals, hub nuts and split pins, that's why wheel bearings are usuall sold as a kit so that you have eveything you'll need to complete the job. Be sure to check out our video for a DIY to how it's done.